The present invention, in some embodiments thereof, relates to systems and methods for treating blood vessels or grafts, and in particular to dilatation balloon catheters for dilating and/or recanalizing occluded or narrowed vein portions and/or vascular accesses.
ESRD (end-stage renal disease) patients amount to about 3 million worldwide, out of which approximately 2 million undergo periodic hemodialysis treatments. Hemodialysis requires a vascular access, a site on the body where blood is removed and returned during the dialysis process. The most common accesses are the arteriovenous (AV) fistula, and the AV graft. Complications of clogging and stenosis occur with high percentages, causing low blood flow at the access site and risking the dialysis process. A regular checkup and assessment of the access is required. Once a problem of low blood flow is identified due to access narrowing, an angioplasty procedure is required to recover normal blood flow. If a blood clot is occluding the access, commonly associated with synthetic grafts, the treatments include thrombectomy and/or thrombolysis. Dialysis access procedures are performed several times per day per operator. Current techniques are time consuming and force the medical practitioner to extended exposures to x-ray radiation.
A venous flow obstruction or stenosis, commonly found in the graft-vein or vein-artery anastomosis of the arteriovenous fistula, causes slow down or obstruction of blood flow, which may result in the formation of thrombus within a graft. Stenotic vein portions may also be found at locations remote from the anastomosis such as in the brachicephalic vein. Usually mechanical thrombolysis means and/or administration of clot dissolving thrombolytic agents is used. After clot dissolution, the patient is typically analyzed under fluoroscopic imaging of the graft to identify and visualize residual venous stenosis. Angioplasty of the stenosed segment can then be performed, using dedicated high pressure dilatation balloon catheters, optionally followed with implanting a stent in order to keep opened areas that are prone to restenosis.
The cephalic vein or basilic vein, which are most common in vascular recanalization of hemodialysis accesses, are substantially large conduits, usually 3 to 6 mm in diameter, demanding high pressure dilatations of 15 atmospheres or more, and in some instances require the use of high pressure ultra-noncompliant dilatations of 25 atmospheres or more. Therefore, specially designed and sized angioplasty or PTA balloon catheters were developed for such specific indications, including, for example, the Kevlar balloon based Conquest® PTA dilatation catheter (of CR Bard; Covington, Ga.), provided in nominal inflation diameters between 5 mm and 12 mm, and with rated burst pressures between 20 atm and 30 atm.
Before and/or during the angioplasty procedure, blood thinners are administrated to prevent formation of blood clots in the conduit during prolonged angioplasty. The blood thinners in dialysis patients carry a risk of bleeding in different areas in the body including at the access sites to the fistula or graft. Having the option to reduce or eliminate the necessary dose of blood thinners will greatly improve patient safely as well as operators' convenience and satisfaction. Less time will be needed for hemostasis at the end of the procedure.
In order to position the balloon adjacent the stenosis and evaluate the result of the angioplasty, a contrast medium is administered to facilitate visualization under fluoroscopic imaging. In common practice, in order to administer the contrast medium adjacent the stenotic region following angioplasty, the dilatation balloon is withdrawn and is replaced with an occlusion balloon for blocking unwanted flow direction of the contrast medium. An occlusion balloon, as opposed to a high pressure dilatation balloon, is made substantially compliant in order to take a shape according to local surrounding boundaries. Inventor Michael Tal in U.S. Pat. No. 7,182,755 “METHOD AND APPARATUS FOR TREATMENT OF THROMBOSED HEMODIALYSIS ACCESS GRAFTS”, the disclosures of which is fully incorporated herein by reference, describes a balloon catheter comprising “a catheter body with a compliant balloon secured at a distal end of the catheter body, a single aperture positioned proximally of the balloon, a first lumen extending through the catheter body and in fluid communication with the balloon for selectively inflating and deflating the balloon, and a second lumen extending through the catheter body and in fluid communication with the aperture for dispensing solution therethrough.”
The need to replace the angioplasty balloon with an occlusion balloon for administering contrast medium is cumbersome and time consuming and even less efficient if further dilatation sessions are needed. This is especially important in angioplasty procedures involving the use of delivering or eluting drug with the angioplasty catheter, used for prevent or diminish restenosis in the recanalized vascular portion, with or without a stent deployed in-place, which usually involve repeated or continuous dilatation for prolonged durations greater than 1 minute, and more commonly 3 minutes or more.
Problems associated with current vascular access recanalization thus include: use of multiple catheters and multiple device exchanges, each associated with additional radiation to visualize position of each catheter; rapid blood flow in the access limits visualization of the blood vessels and requires repeated contrast injections and angiograms; risk of clot migration to artery when performing de-clotting procedure.
There is thus a need to introduce multi-functional balloon catheters dedicated to angioplasty and/or occlusion that also include means for fluids dispersion (medicaments and declotting agents, flushing media and/or contrast enhancing media) for facilitating improved techniques that can lower number of procedural steps, treatment time and radiation exposure. There is also a need to decrease overall amount of contrast enhancing media injected per session. There is also a need to inject contrast enhancing media into a clogged access for whole access visualization while declotting, therefore diminishing the risk of clot migration to the artery.